That is a good point, if all he wants is layering, an ortho view is probably easier.
He said he wanted 2D with layers, so your w and d, or my xrange and zrange, will necessarily have to be recalculated for each Z. An orthographic projection still allows layering and depth, but there's no need to recalculate anything for different depths, and the coordinate system can be directly and explicitly specified with the desired ranges. That is why I ultimately asked the question if his perspective approach is really necessary, or just based on the no-so-uncommon erroneous belief that your program cannot have multiple types of projections.
I'm not sure what he wants from the original question, so hopefully he is properly helped now with our combined perspectives